Lower call stack size for test_big_recursive_cobegin

This recursively creates 1024 tasks, and at the default of 8MB per task that's
8GB of memory. Trying to limit max memory used by correctness tests to under
4GB so I'm lowering the call stack size
Lower call stack size for parallel/taskPool/figueroa/ManyThreads

This recursively creates up to 3000 tasks, and at the default of 8MB per task
that's a lot of memory. I'm trying to limit max memory used by correctness
tests to under 4GB so I'm lowering the call stack size
Merge pull request #387 from ronawho/qthreads-testing

Lower call stack size for test_big_recursive_cobegin and ManyThreads

[trivial, not reviewed]

Both of these tests fail on some of our machines that have ~4GB of memory. Both create a lot of tasks which means a lot of stacks. With qthreads these tasks are being created faster than they were with fifo which means they might use more memory at any given moment (same amount of memory used total though.) In general I've been trying to lower correctness tests to use at most 4GB of ram.

Even though there are a lot of tasks I think we can leave guard pages on, as they don't seem to have any real performance impact for these two (both tests finish in fractions of a second.)